SYNTHESIS AND PROPERTIES OF POLYSTYRENE／LAPONITE NANOCOMPOSITES

Exfoliated polystyrene (PS)/laponite nanocomposites were prepared successfully. The characteristic doo1 diffraction peak of organo-laponite disappeared in the XRD patterns of nanocomposites, indicating that the laponite layers were exfoliated and the ordered crystal structure of laponite was destroyed because of the styrene polymerization. TEM observations showed that the exfoliated laponite primary particles were dispersed randomly in the PS matrix with lateral dimensions from 1 nm to 10 rim. SEM results showed that the PS/laponite nanocomposite particles were almost monodispersed spheres with the size of about 120 rim. Because of the interaction between PS and laponite nanolayers, the nanocomposites exhibited higher thermal stability and glass transition temperature when compared to pure PS.     

Effect of pH on the Hydrothermal Synthesis of BN Nanocrystals

Boron nitride (BN) has been synthesized using hydrothermal synthesis method. The experimental results showed that the pH value of the reaction solution has an important effect on the yield and phases of BN samples. As the pH value decreased, the content of cBN increased and the yield improved. The increase in cBN content is resulted from the conversion of oBN into cBN under hydrothermal condition, and the growth of cBN nanocrystals may due to the decrease in the reaction speed, thus the crystalline perfection of BN improved when the pH value decreased.     

Synthesis of Ni／Mg／Al Layered Double Hydroxides and Their Use as Catalyst Precursors in the Preparation of Carbon Nanotubes

Ni/Mg/Al layered double hydroxides(LDHs) with different n(Ni) : n(Mg) : n(Al) ratio values were prepared via a coprecipitation reaction. Then Ni/Mg/Al mixed oxides were obtained by calcination of these LDHs precursors. Carbon nanotubes were produced in the catalytic decomposition of propane over the Ni/Mg/Al mixed oxide catalysts. The quality of as-made nanotubes was investigated by SEM and TEM. The nanotubes were multiwall with a high length-diameter ratio and appeared to be flexible. The catalytic activities of these mixed oxides increased with increasing the Ni content. The Ni/Mg/Al mixed oxide with the highest Ni content [ n( Ni)/n( Mg)/n(Al) = 1/1/1 ] showed the highest activity and the carbon nanotubes grown on its surface had the best quality.     

A STUDY ON MECHANICAL PROPERTIES OF γ-RAY IRRADIATED HDPE FILLED WITH SERICITE-TRIDYMITE-CRISTOBALITE*

The effect of γ-ray irradiation on the mechanical properties of high densitypolyethylene(HDPE) filled with sericite-tridymite-cristobalite(STC) was studied. The ex-perimental results show that γ-ray irradiation can improve the affinity between HDPE andSTC, and the dispersion of STC in HDPE matrix. Compared with HDPE/STC (80/20)blend, the yield stress and impact strength of irradiated HDPE (10kGy)/STC (80/20) blendare increased from 22.8 MPa and 70J/m to 28.5 MPa and 144J/m. The yield stress andimpact strength of HDPE/irradiated HDPE/STC (48/32/20) are 27.8MPa and 210J/m,respectively.     

PREPARATION OF POLY（METHYL METHACRYLATE）/LAYERED DOUBLE HYDROXIDES NANOCOMPOSITES via in situ SOLUTION POLYMERIZATION

An exfoliated layered double hydroxides/poly(methyl methacrylate)(LDHs/PMMA)nanocomposite was prepared by in situ solution polymerization of methyl methacrylate(MMA)in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs).MgAl-VBS LDHs was prepared by the ion exchange method,and the structure and composition of the MgA1-VBS LDHs were determined by X-ray diffraction(XRD),infrared spectroscopy and elemental analysis.XRD and transmission electron microscopy(TEM)were employed to examine the structure of LDHs/PMMA nanocomposite.It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix.The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased.     

VISCOELASTIC BEHAVIOR OF THE NON-HOOKE DEFORMATION BEFORE YIELDING IN UNIAXIAL DRAWING OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE)*

Viscoelastic behavior of the non-Hooke deformation of amorphous PET film before yield was investigated in thetemperature region 74--80.5℃ around the glass transition temperature. The film specimen was drawn to yield point followedby unloading to zero stress, then the residual deformation was held constant, while the subsequent evolution of the stress wasrecorded. An induction period was found in the course of stress evolution fol1owed by a stress step-increase. The inductionperiod decreases with increasing drawing temperature with an activation energy of 1.10 MJ/mol·K, which is attributed tothe time needed for the relaxation of rubbery deformation through cooperative internal rotations. At temperatures lower than74℃, there is no stress increase or the induction period becomes too long to be observed. Thus the nature of anelasticity inthe non-Hooke region before yielding is attributed to stress induced rubbery deformation. The experimental results areinterpreted in terms of Perez' rheological model of a series connected Hooke spring and a Voigt element consisting of aparallel connected elastic spring and a dashpot.     

Molybdosphoric Acid Mixed with Titania Used as a Catalyst to Synthesize Diphenyl Carbonate via Transesterification of Dimethyl Carbonate and Phenol

The 12-molybdosphoric acid mixed with titania (MPA-TiO2) was found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) via transesterification of dimethyl carbonate (DMC) and phenol. The X-ray diffraction (XRD) and infrared (IR) techniques were employed to characterize the prepared catalysts. The effect of the weight ratio of the 12-molybdosphoric acid to titania on the transesterification was investigated. A 13.1% yield of DPC and an 11.6% yield of methyl phenyl carbonate (MPC) were obtained over MPA-TiO2 with the weight ratio of MPA to TiO2 as 5:1.     

Study on the Synthesis of Phenylacetic Acid by Carbonylation of Benzyl Chloride under Normal Pressure

The influences of some factors on the yield of phenylacetic acid in the carbonylation of benzyl chloride were studied in this paper. These factors included the variety and content of catalyst, and that of solvent, way of material feeding, reaction temperature, sodium hydrate concentration, triphenylphosphine content, presence of surfactant, the ratio of organic phase volume to aqueous phase volume etc. The optimum reaction conditions were found to be: with a one-time pour of 0.15g Pd(PPh3)2Cl2, 0.24g PPh3, 75ml NaOH of 3.5mol/L, 20ml benzyl chloride and 55ml n-butyl alcohol, and the reaction was carried out at 50℃ for about 3 hours. The as-obtained yield of phenylacetic acid was as high as 97.6%. In addition, the influences of the presence of phenylacetic acid and air in the reaction system were also studied. The results showed that the presence of air in the system and the entrainment of phenylacetic acid in the circulating organic phase had great influence on the reaction rate, the stability and performance of catalyst and the yield of phenylacetic acid.     

In situ catalytic conversion of biomass fast pyrolysis vapors on HZSM–5

In situ catalytic conversion of biomass fast pyrolysis vapors was carried out on HZSM-5 with varying Si/Al ratios(ranging from 20 to 300) at 450 °C. The effects of Si/Al ratios of HZSM-5 zeolites on the distribution of biomass fast pyrolysis products and carbon deposits on catalysts were investigated. It was quite remarkable that after in situ catalytic conversion the amount of light phenols and hydrocarbons increased significantly while that of heavy phenols decreased a lot. Besides, the yield of cyclopentenones with relatively low oxygen content generally increased. It also indicated that as the Si/Al ratios of HZSM-5 increased, the amount of hydrocarbons and light phenols was found to drop greatly. The amount of carbon deposits was found to be around 8.5% with the exception of HZSM-5 with the Si/Al ratio of 300,which is much lower. Moreover, the carbon deposits yield dropped gradually with increasing Si/Al ratios of HZSM-5.Calcination of spent catalysts at 600 °C helped to restore the catalytic activity to a large extent despite a relatively lower efficiency of deoxygenation. Results indicated that HZSM-5 with relatively high acidity displayed great catalytic performance.     

Enhancement of Overall Photovoltaic Efficiency by Changing the Position of the Attaching Group -RSO3- on the Hemicyanine Dye Molecules

A new photoresponsive D-π-A dye, mPS, has been designed and synthesized.Compared to the parent dye PS, IPCE values in the region from 400 nm to 560 nm was greatly improved upon changing the attaching group from the p- position to the o- position of the π-conjugation bridge. A solar cell based on mPS generated a remarkably high overall yield η of 5.4% under irradiation of 80.0 mW cm^-2 white light from a Xe lamp, Compared with PS, the overall yield η increased by 64%.     

己二酸柱撑水滑石的制备及表征

水滑石（Layered Double Hydroxidex,简称LDHs）是一类具有层状结构的阴离子型粘土^[1]。水滑石的一个重要性质是层间阴离子具有可交换性,引入不同的阴离子,能够得到不同结构和功能和柱撑水石滑,因而阴离子插层是水滑石研究的一个重要方向。各类阴离子如有机和无机阴离子、同多和杂多阴离子以及金属配合物阴离子的柱撑水滑石在文献中都有报道^[2-5]。其中有机阴离子由于在结构上的多样性,使有机阴离子柱撑水滑石具有巨大的应用开发潜力,已经引起了人们的广泛关注^[6-12]。     

乳液聚合法制备聚苯乙烯/Mg-Al层状双氢氧化物纳米复合材料

采用乳液聚合法制备阻燃性聚苯乙烯MgAl层状双氢氧化物(LDHs)纳米复合材料.通过对不同合成条件下复合材料的XRD谱,讨论了纳米复合材料的形成过程;经SEM图证实了LDHs是以剥离的纳米级层片分散在基体中的;TG和DSC谱图揭示了LDHs纳米层板可有效提高PS的热稳定性,并可使PS的玻璃化转化温度明显提高;当层状双氢氧化物在插层复合材料中含量为14.92%时,纳米复合材料的氧指数可达23.5%,其用量比在PS中直接添加纳米LDHs时要少约一倍.文中还分析了纳米复合材料的形成过程.     

新原料路线共沉淀法组装超分子结构柠檬酸根插层水滑石

以Mg(OH)₂和NaAlO₂为原料，采用新原料路线共沉淀法实现了柠檬酸根插层结构LDHs的超分子组装。用XRD、FT-IR、TG-DTA和元素分析等手段对样品进行分析表征。结果表明，新原料路线共沉淀法较常用的共沉淀法得到的柠檬酸根插层LDHs结晶度高、晶相单一，客体柠檬酸根在LDHs层间的排列高度有序。     

Study of assembly of arachidic acid/LDHs hybrid films containing photoactive dyes

Hybrid monolayers formed with an floating arachidic acid (AA) anions monolayer binding with a densely packed layered double hydroxides (LDHs) monolayer at an air/LDHs suspension interface has been studied by pi-A isotherms and TEM images. An ordered multilayer film of AA/LDHs has been fabricated by Langmuir-Blodgett technique on various substrates. The photoactive dyes (methyl orange, MO, and Congo red, CR) can be incorporated into the galleries of LDHs in the AA/LDHs hybrid LB film by an ion intercalation method. The results of FTIR and UV-vis absorption spectra can approve the formation of AA/LDHs/dyes composite films. In addition, UV-vis absorption spectra and LAXRD analyses also provide evidence for the good vertical uniformity and stable layered periodic structure of AA/LDHs/dyes films. More interestingly, it was found that the dye molecules intercalated can be induced by a positively charged LDHs sheet to align in a special orientation and form different aggregates: MO molecules form sandwich H-type aggregates, while CR molecules form head-to-tail J-type aggregates. On the basis of these data, a possible model of the AA/LDHs/dyes composite films was proposed. Also, the dye molecules incorporated into AA/LDHs films exhibit excellent configuration stability under the irradiation of UV light because the LDHs matrix offers a more rigid and constrained environment for them.     

MgAlZnFe-CO3 LDHs对PBS膨胀阻燃体系性能的影响

采用恒定pH值共沉淀法在自制反应器中合成了不同原料配比的碳酸根型镁铝锌铁层状双羟基金属氧化物（MgAlZnFe-CO₃ LDHs）,并通过熔融共混MgAlZnFe-CO₃ LDHs、聚磷酸铵（APP）、三聚氰胺（MA）和全降解材料聚丁二酸丁二醇酯（PBS）制备出PBS膨胀阻燃材料. 采用傅里叶红外光谱（FTIR）、热失重（TG）、X射线衍射（XRD）、扫描电子显微镜（SEM）及元素分析（ICP）对MgAlZnFe-CO₃ LDHs进行了表征,并对PBS膨胀体系进行了力学性能和阻燃性能等测试. 结果表明,当Mg²⁺,Zn²⁺,Al³⁺和Fe³⁺的摩尔比为9：3：3：1时,合成的MgAlZnFe-CO₃ LDHs热稳定性最好,晶态结构规整,呈形貌规则的六边形片状;当MgAlZnFe-CO₃ LDHs的添加质量分数为1%时（阻燃剂的总添加质量分数为20%）时,PBS膨胀阻燃体系的极限氧指数（LOI）达到35%,垂直燃烧测试达到UL-94 V-0级别,力学性能得到较大改善. 实验结果表明,低添加量的MgAlZnFe-CO₃ LDHs与膨胀阻燃剂（IFR）协效阻燃PBS,一方面能够改善膨胀阻燃剂恶化PBS力学性能的现象,另一方面协同效应能够明显提高PBS的阻燃性能.     

Synthesis of heptamolybdate‐intercalated MgAl LDHs and its application in polyurethane elastomer

Heptamolybdate (Mo₇O₂₄^6?) was intercalated in the interlayer space between MgAl‐layered double hydroxides (Mo‐MgAl LDHs) by the hydrothermal and ion exchange method, and then polyurethane elastomer (PUE) based composites were prepared by the prepolymerization method with different amounts of Mo‐MgAl LDHs. X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, laser Raman spectroscopy (LRS), and scanning electron microscopy (SEM) were employed to characterize the obtained LDHs. The performance of the PUE/LDHs were evaluated by measuring their thermal gravimetric, heat release rate (HRR), and smoke density (Ds). The results show that PUE/LDH composites exhibit a lower peak heat release rate (pk‐HRR), Ds, and a prolonged combustion time, in comparison with neat PUE. Comparison between NO₃‐MgAl LDHs and Mo‐MgAl LDHs containing composites show that the introduction of Mo⁶⁺ is able to facilitate flame retardance and smoke suppression efficiency, which results mainly from the presence of MoO₃ derived from the decomposition of Mo₇O₂₄^6? intercalated LDHs. Mo‐MgAl LDHs reduce the pk‐HRR of composites by 39% with only 1 wt.% content, and the maximum Ds of composites is reduced to a minimal value of 274 with 10 wt.% Mo‐MgAl LDHs. More importantly, LDHs would improve the mechanical properties at a low content. The experimental results reveal the potential of Mo₇O₂₄^6? intercalated LDHs to improve both the flame retardancy and smoke suppression of PUE. Copyright © 2015 John Wiley & Sons, Ltd.     

纳米晶Mg-Al水滑石的水热合成及微结构表征

Nano Mg-Al LDHs were prepared from precursors of MgO and Al(OH)₃ using a hydrothermal method in one step and the microstructural features were characterized by powder XRD and SEM. Crystallite sizes were determined by X-ray whole powder pattern fitting method. Effects of synthesis temperatures and alkalinity on phases formation、crystallinity and crystallite sizes of Mg-Al LDHs were investigated. Crystallite form evolved from thin plates to thick plates as the hydrothermal synthesis temperature increases. Layers of interlayer containing OH^- and CO₃^2- were distributed orderly or disorderly depending on the the starting alkalinity of the precursors along the c axis resulting in an interstratified Mg-Al LDHs structure.     

Preparation and characterization of microencapsulated LDHs with melamine‐formaldehyde resin and its flame retardant application in epoxy resin

Layered double hydroxides (LDHs) are emerging as a new and green high‐efficient flame retardant. But LDHs aggregate seriously because of their hydrophilicity, which affect deeply the mechanical and flame retardant properties of their composites. For the first time in this paper, microencapsulated LDHs (MCLDHs) with melamine‐formaldehyde (MF) resin were prepared by microencapsulation technology to enhance their compatibility and dispersion within epoxy resin (EP). The mechanical and flame retardant performances of EP/MCLDH composite were studied by comparing with EP/LDH composite. Results showed that the water contact angle of MCLDHs increased from 8.9° to 122.1°, which indicated good compatibility. The particle size of MCLDHs decreased sharply, and more than one‐third were up to submicron scale, which can be conducive to dispersion. Moreover, the tensile strength and elongation at break of EP/MCLDHs with different flame retardant contents were higher than those of EP/LDHs. And the addition of MCLDHs increased the glass transition temperature (Tg) of EP/MCLDHs, which meant a strong interfacial interaction. Besides, compared with EP/LDHs, the limiting oxygen index values of EP/MCLDHs were higher, and its peak of heat release rate and total heat release decreased by 16.3% and 5.5% respectively. EP/MCLDHs achieved from V‐1 to V‐0 rate with the increasing content of MCLDHs from 20% to 30%, while LDHs/EP never passed tests. In the process of heating, H₂O, CO₂, and NH₃ released from MCLDHs formed gaseous phase, and the remaining dense char layers and oxides produced condensed phase, which played an important role in inhibiting combustion.     

Preparation and characterization of polystyrene (PS)/layered double hydroxides (LDHs) composite by a heterocoagulation method

Polystyrene (PS)/layered double hydroxides (LDHs) composites were prepared for the first time from LDHs aqueous suspension and PS emulsion by electrostatic assembly. The morphology characterization based on XRD and TEM showed that the LDHs were partially exfoliated in PS matrix. By using a reactive emulsifier, i.e., sodium 2-hydroxyl-3-(methacryloxy)propane-1-sulfonate (HMPS), which was able to copolymerize with styrene, a strong polymer-LDHs platelets interaction was achieved. The glass transition temperature (T _g ) of the composites was measured by DSC and DMA. The results showed that a strong polymer-LDHs platelets interaction played a dominant role in affecting the mobility of polymer chains, i.e., the T _g . With a strong interaction, PS-HMPS/LDHs composite showed a significant enhancement in T _g while a slight increase in T _g was observed for PS-SDS (PS prepared by emulsion polymerization using sodium dodecyl sulfate as emulsifier)/LDHs composite with a weak interaction. The addition of LDHs improved the thermal stability of PS, and the improvement depended on the dispersion of the LDHs platelets.     

电化学形成的PtFeNi合金与含缺陷NiFe LDHs载体之间的电荷转移实现高效水分解

氢气是一种能量密度高,可完全燃烧的清洁能源.发展绿色制氢技术对于解决全球环境污染,二氧化碳排放等环境问题具有重要意义.电化学水分解被认为是一种清洁高效的制氢手段,可自恰于可再生能源的波动性,具有效率高、响应快、氢气纯度高等优点.然而,由于电化学反应过电位大及动力学缓慢的原因,驱动电化学水分解的能量消耗巨大.因此,开发高...